Theoretical models of the coupled ionosphere-plasmasphere system have been investigated with respect to processes occurring in the nighttime F2 layer. It is found that plasma flow from the plasmasphere into the ionosphere has a strong stabilizing influence upon the peak F2 region ion density NmF2 such that for wide ranges of applied east-west electric fields or north-south thermospheric winds there is essentially no change in the maximum density of the F2 layer (NmF2). It is also found that NmF2 depends sensitively upon the plasma density of the plasmasphere and upon the neutral hydrogen concentration in the thermosphere. Time-dependent processes have been studied also by using step function electric fields and neutral winds. In the electric field case, squeezing of thermal plasma out of the plasmasphere along a contracting field tube significantly affects NmF2. Neutral thermospheric winds, on the other hand, have little effect on nighttime NmF2.